Dialkylsalicylic acids and alkaline earth metal salts thereof

ABSTRACT

ALKYLSALICYLIC ACIDS HAVING A HIGH DEGREE OF PARA-SUBSTITUTION AND HAVING THE ALKYL GROUP ATTACHED TO THE BENZENE NUCLEUS BY A QUATERNARY CARBON ATOM ARE PREPARED FROM TERTIARY ALKYLATING AGENTS AND IN PRATICULAR BY A TWO STAGE ALKYLATION OF PHENOL USING A STRAIGHT CHAIN MONOOLEFIN IN THE FIRST STAGE AND A BRANCHED MONOOLEFIN IN THE SECOND STAGE. THE POLYVALENT METAL SALTS OF SAID ACIDS ARE EXCELLENT LUBRICANT AND FUEL ADDITIVES CHARACTERIZED BY IMPROVED HIGH TEMPERATURE PERFORMANCE, THE ABILITY TO KEEP THE INTERIOR OF ENGINE CYLINDERS CLEAN AND TO COUNTERACT DEPOSITION OF CARBONACEOUS MATTER ON PISTONS AND PISTON RING GROOVES.

United States Patent 3,704,315 DIALKYLSALICYLIC ACIDS AND ALKALINE EARTH METAL SALTS THEREOF Aart Strang, Amsterdam, Netherlands, assignor to Shell Oil Company, New York, N.Y.

No Drawing. Filed Dec. 17, 1969, Ser. No. 885,982 Claims priority, application Great Britain, Dec. 19, 1968, 60,355/68 Int. Cl. C07c 65/12 US. Cl. 260-521 R 4 Claims ABSTRACT OF THE DISCLOSURE Alkylsalicylic acids having a high degree of para-substitution and having the alkyl group attached to the benzene nucleus by a quaternary carbon atom are prepared from tertiary alkylating agents and in particular 'by a two stage alkylation of phenol using a straight chain monoolefin in the first stage and a branched monoolefin 'm the second stage. The polyvalent metal salts of said acids are excellent lubricant and fuel additives characterized by improved high temperature performance, the ability .to keep the interior of engine cylinders clean and to counteract deposition of carbonaceous matter on pistons and piston ring grooves.

BACKGROUND OF THE INVENTION This invention, therefore, relates to alkylsalicyclic acids and their polyvalent metal salts as novel compounds and to processes to prepare these compounds. The invention particularly relates to the application of basic polyvalent compounds as additives in lubricants and fuels.

British Pat. 1,146,925 relates to lubricant compositions with improved dispersant properties at high temperatures, comprising one or more lubricants and one or more salts of polyvalent metals and alkylsalicylic acids, which alkylsalicylic acids contain at least one alkyl group having more than 12 carbon atoms and of which more than 60% m. consists of acids with an alkyl group that is attached to the benzene nucleus in para-position relative to the hydroxyl group.

As possible modes of preparation for these salts the specification pertaining to the said application describes four routes starting from phenol, orthoand para-cresol and salicylic acid. The one starting from phenol is economically the most attractive. Phenol is alkylated with cetene and the alkylphenols thus obtained are converted into the corresponding alkylsalicylic acids by phenation,

carboxylation and hydrolysis. This process yields a mixture of alkylsalicylic acids of which 88% m. contains an alkyl group that is attached to the benzene nucleus in para-position-relative to the hydroxyl group. These acids can be converted via conventional methods into the .desired salts.

For the preparation of the salts on a large scale the use of pure cetene as alkylation agent is less attractive economically. Olefin mixtures seem to be better suited and according to examples given in the aforementioned specification, satisfactory results can be obtained with contains a high proportion of salts of 3-alkylsalicylic acid originating from the 2-alkylphenol. As described in the aforementioned specification, the latter salts, atterinice corporation in a lubricant, do not show a significant improvement in dispersant properties at high temperatures over mixtures of salts of polyvalent metals and alkylsalicylic acids already known.

Etforts to find a suitable way to decrease the quantity of 2-al-kylphenol in the alkylate have heretofore failed. For example, the quantity of 2,4-dialkylphenol was increased at the cost of the quantity of 2-alkylphenol, formed during alkylation by applying more severe alkylation conditions (higher alkylation temperature and large excess of olefins). However, this only led to an increase in the percentage of noncarboxylatable 2,4,6-trialkylphenol in the alkylate, while the yield of.2,4-dialkylphenol hardly increased. Another possibility investigated was the separation of the Z-alkylphenol from the mixture of alkylphenols. The separation, which calls for a highvacuum distillation and is relatively expensive, leads only to the separation of mono and dialkylphenols, so that .not only the undesired 2-al=kylphenol, but also the 4-alkylphenol, which is suitable for further conversion into alkylsalicylic acid, is removed from the alkylphenol mixture.

SUMMARY OF THE INVENTION It has now been found that in the preparation of alkylsalicylic acids by alkylation of phenol followed by phenation, carboxylation, and hydrolysis the formation -of a substantial amount of 3-alkylsalicylic acid can be prevented if the alkylation is completely or partly carried out with an alkylation agent which attaches preferentially to the benzene nucleus in para-position relative to the hydroxyl group. These alkylation agents have such a structure that the alkyl group attaching'to the benzene nucleusis attached to it with a quaternary carbon atom. The acids so obtained and their corresponding salts subsequently obtained are novel compounds.

The invention, therefore, relates to salts of polyvalent metals and alkylsalicylic acids containing at least one alkyl group having more than 12 carbon atoms and having an alkyl group in the para position relative to the hydroxyl group, the para positioned alkyl group being attached to the benzene nucleus by a quaternary carbon atom.

Alkylation agents having such a structure that the alkyl group which attaches to the benzene nucleus is attached to it with a quaternary carbon atom, will for the sake of brevity be indicated hereinafter as tertiary alkylation agents. Generally at least 25% m. and preferably 30% in. of the para-positioned alkyl groups are attached- .polyisobutenes, triisopentene and higher polyisopentenes,

diisooctenes and higher polyisooctenes etc. or precursors for these olefins such as monohydroxyalkanes in which the hydroxyl group is attached to a tertiary carbon atom or occurs in an a-position relative to a tertiary carbon atom in the molecule.

The alkylation of phenol is preferably carried out in two stages using a different alkylation agent in each stage,

one of which is a-tertiary alkylation agent having from 4 to 12 carbon atoms-in the molecule and the other an alkylation agent containing a hydrocarbon group having from 12 to 30 carbon atoms. Examples of suitable tertiary alkylation agents are in this case monoolefins having from 4 to 12 carbon atoms in the molecule which are branched at one or both of the carbon atoms adjacent to the double bond, or precursors'for these olefins. Very suitable are monoolefins with the general formula RC(CH )=.CH

in which R represents an alkyl group having from 1 to 9 carbon atoms. Examples of such monoolefins are isobutene, isopentene and isohexene. Particularly suitable is isobutene. Examples of suitable alkylation agents which can be used in combination with the above-mentioned tertiary alkylation agents are straight-chain olefins having from 12 to 30 carbon atoms in the molecule, for example tridecene, tetradecene, pentadecene, etc. Mixtures of such straight-chain monoolefins are very suitable, in particular such olefin mixtures obtained in cracking straight-chain paratl'ins, e.g. straight-chain'parafiins obtained by means of urea extraction or by selective separation by means of molecular sieves.

In general, olefins suitable for alkylation have less than about 50 carbon atoms and preferably less than 25 carbon atoms.

Alkyl groups attached with a quaternary carbon atom to the benzene nucleus, such as tertiary butyl groups, show the tendency to shift under the prevailing alkylation conditions (for example a shift from the para to the ortho position). This shift is proportionally greater the longer the alkylate is in contact with the alkylation catalyst. Since the two-stage alkylation of phenol has as its primary purpose a maximum yield of para-substituted material,

the contact between the para-tert-alkylphenol and the alkylation catalyst should be as short as possible. In this connection the two-stage alkylation of phenol as hereinbefore described is preferably carried out in such a way that the tertiary alkylation agent is applied in the second kinds of clays. However, the most frequently used clay catalysts come from naturally occurring sources, such as bentonites composed of montmorillonite, from halloysites, and from kaolinite clays.

The specific type of clay used is not very critical if the clay selected is low in iron content and substantially free from various elements such as heavy metals which would favor either poisoning of the catalyst or the production of undesired products. Both pellet or fluid powder forms can be used. The clays are usually activated by treatment with a mineral acid, such as sulfuric, at

moderately elevated temperatures.

The alkylation of phenol with straight-chain monoolefins having from about 12 to 30 carbon atoms in the molecule is preferably carried out at temperatures between 175 and 225 C., preferably with 0.6 to 1.0 mole of olefin per mole of phenol.

The alkylation of the alkylphenols with branched monoolefins having the general formula RC(CH )=CH in which R represents an alkyl group having from 1 to r 9 carbon atoms, is preferably carried out at temperatures between 50 and 200 C., preferably with 1.0 to 1.5 mole of olefin per mole of alkylphenol.

The conversion of the alkylphenols thus prepared into -the corresponding alkylsalicylic acids can be elfected according to any of the techniques known in the art. One suitable technique is as follows: I

Using an alcoholic caustic solution the *alkylphenols are converted into the corresponding alkylphenates, which 7 are then treated with CO at about 140 C. and'a pressure of 10 to 30 atm., the alkylsalicylic acids are obtained from the alkylsalicylates by using, for example, a 30% sulphuric acid solution.

The salts according to the invention are suitable for use as additives in lubricants and fuels. They are of special importance as additives in lubricating oils, because they are capable of keeping the interior of engine cylinders, in particular diesel engine cylinders, clean, and of counteracting deposition of carbonaceous products on pistons and in piston ring grooves.

When the salts according to the invention are used as .lubricant additives, basic salts are preferable because these salts, in addition to their dispersant action, are capable of neutralizing acid compounds formed during the combustion process in the engine. A basicity up 'to about 250% is in most cases suflicient. Favorable results can, however, be obtained by using polyvalent metal salts of the present type with a basicity between 25 and 225%, e.g. polyvalent metal salts with a basicity of about 50% or of about 200%. Particularly eligible among the salts of polyvalent metals and alkylsalicylic acids as lubricant oils additives are the salts of bivalent metals. Preference is given to salts of Group II metals, particularly alkaline earth metals and most particularly to calcium salts.

Therefore, the preferred salts are the basic barium, calcium, magnesium and strontium salts.

The conversion of the alkylsalicyclic acids into neutral as well as basic salts can be effected according to techniques generally known and used for such conversions. For the preparation of neutral calcium salts the alkylsalicylic acids can, for example, be converted into the corresponding sodium salts, which are then allowed to react with an equivalent quantity of CaCl For the preparation of basic calcium salts with a relatively low basicity, for example 5 0%, one can treat the alkylsalicylic acids with two equivalents of calcium in the form of Ca(OH) For the preparation of basic calcium salts with a higher basicity, for example 200%, the alkylsalicylic acids can be treated with four equivalents of calcium in the form of Ca(OH) while introducing 1.6 equivalents Of C02.

The basicity of these metal salts is usually defined as the excess of metal in the basic salts over that quantity of metal which would be present in the normal (nonbasic) salts alone. Thus a mixture of 0% basicity would denote a mixture containing the metal only in the form of the normal salt and a mixture of basicity would denote a mixture containing twice as many equivalents of the metal as the number of equivalents of replaceable acidic hydrogen atoms in the acid. If the content of metal in a particular mixture is (a) percent by weight, and if the content of metal the mixture would have if it were present only as the normal salt is (b) percent by weight then the basicity of the mixture is As stated hereinbefore, the metal salts preferably should be derived from alkylsalicylic acids containing at least one alkyl group with more than 12 carbon atoms. For application in lubricant oils metal salts of alkylsalicylic acids containing at least one alkyl group with at least 14 carbon atoms, such as metal salts of alkylsalicylic acids containing an alkyl group with 15-18 carbons are preferable.

With respect to the molar percentage of the acids containing an alkyl group attached to the benzene nucleus in para-position relative to the hydroxyl group, alkylsalibelonging to S.A.E. grades from SWto 70W are accep'table. Suitable oils can also be derived from highly paraflinic or highly napthenic oils with substantial amounts or aromatics. Chemical or selective solvent treatment can be used if desired. Mixed base crudes and highly aromatic crudes containing parafiinic hydrocarbons are also suitable base'stocks after refining.

The mineral oil bases can be blends of distillate lubricating oils and bright stocks or they can be mixed with, or even entirely replaced by, synthetic lubricants or polymerized olefins such as polyisobutylene. The polyvalents salts of the invention can also be added to lubricating greases. The salts of the polyvalent metals and the alkylsalicylic acids can be incorporated as suchin the lubricant or in the form of a concentrate that has been obtained, for example, by mixing the salts withasmall quantity of oil. I v

The concentration of the present metal salts in the lubricant can vary within wide limits. The salts-are generally present in such amounts as to give an average T. B.N.E. in the range of 5-12 preferably 6-10. In general, the desired dispersancy is obtained if the lubricants contain 0.01 to 5% w., in particular 0.1 to 1% w. of polyvalent metal in the form of the instant salts of polyvalent metals and alkylsalicylic acids.

In addition to the salts of the polyvalent metals and the alkylsalicylic acids, the lubricant compositions may contain other additives, such as antioxidants, foam inhibitors, anticorrosion agents, viscosity and/or viscosity index improvers, agents to improve the lubricating action and other substances which are usually added to lubricants. It is desirable to use relatively small amounts of other additives, e.g. from 0.01 to about 2% by weight of the composition. These examples are in no way meant to limit the number or kind of additives that may be incor porated into lub-ricants in addition to polyvalent metal salts. Any suitable additive desired may be incorporated.

The following series of examples show prior art methods as well as the improved method of the invention of alkylating phenol. Examples A and B are prior art methods. Examples I and II are examples according to the present invention. The C -C olefin mixtures used in Example B, I and II was a mixture of straight-chain monoolefins with 15-18 carbon atoms, in the molecule, obtained in cracking straight-chain paraflins obtained by means of urea extraction.

EXAMPLE A (According to Great Britain Pat. 1,146,925)

Phenol was alkylated at 150 C. with cetene (molar ratio 1:2.5) using 5% w. of acid clay as catalyst. The alkylphenols thus obtained were converted into the corresponding alkylsalicylic acids by phenation, carboxylation and hydrolysis. In this way 1 mol of phenol yielded 0.65 mole of alkylsalicylic acids with the following composition:

12% m. of 3-cetylsalicylic acid 88% m. para-substituted 12% m. of 5-cetylsalicylic acid 76% m. of 3,5-dicetylsalicylic acid EXAMPLE B Phenol was alkylated at 200 C. with a mixture of C C olefins (molar ratio 1225) using 5% w. of acid clay as catalyst. The alkylphenols thus obtained were converted into the corresponding alkylsalicylic acids by phenation, carboxylation and hydrolysis. In this Way 1 mole of phenol yielded 0.50 mole of alkylsalicylic acids with the following composition:

36% m. of 3-(C -C alkylsalicylic acid 64% m. para-substituted 16% m. of 5-(C -C alkylsalicylic acid 48% m. of 3,5-di(C -C alkylsalicylic acid Example I 1.3 mols of phenol, 1.0 mol of a C -C mixture of olefins and-"5% wfof acid clay catalyst (relative to the sum of the quantities .byweight of the alkylation agent and the phenol to be alkylated) were reacted in a first alkylation zone and were added to a glass flask provided with a stirrer, cooling coils and a gas inlet tube. The flask" was heated to 190-210 C. while stirring and bubbling nitrogen through the reactants. In a similar manner the resulting alkylphenols were then alkylated in a second zone withfisobutene (molar ratio 1 to 1.1) again usingv 5% w. of the acid clay catalyst. The alkyl phenols obtained in the second alkylation were reacted, at room temperature and pressure, with an excess alcoholic solution of sodium hydroxide to give the corresponding alkylsodium phe'nates, and then pumped to the top of a steamjacketed absorption column. The absorber operates at a temperature of 160 to 165 C. Dry CO gas was intro- 5% m. of 3-(C -C alkylsalicylic acid m. para-substituted 24% m. of 5-(C -C alkylsalicylic acid acid 9% m. of 3,5-di-(C C dialkylsalicylic acid 38% m. of 3-(C -C alkyl-S-tert. butylsalicylic acid 24% m. of 3-tert. butyl-5-(C -C alkylsalicylic acid Thus, of the para-substituted acids, 40% m. were attached to the benzene nucleus by a quaternary carbon. The alkylsalicylic acids obtained were converted into calcium salts with a basicity of 50 and 200% w. by treating at about 200 C. the alkylsalicylic acids with two and four equivalents of Ca(OH) respectively while adding 1:6 equivalents of CO to the latter. The basic calcium salts so obtained were then recovered by conventional methods.

Example 11 Phenol was alkylated at 200 C. with a mixture of C -C olefins (molar ratio 13:1) with 5% w. of acid clay as catalyst. The alkyl-phenols thus obtained were subsequently alkylated at C. with isobutene (molar ratio 1:1.1), again with 5% w. of acid clay as catalyst. The alkylphenols obtained in this second alkylation were converted into the corresponding alkylsalicylic acids by phenation, carboxylation and hydrolysis. In this way 1 mole of C -C olefins yielded 0.5 mole of alkylsalicylic acids with the following composition:

12% m. of 3-(C -C )alkylsalicylic acid 88% m. para-substituted 18% m. of 5-(C C )alkylsalicylic acid 9% m. of 3,5-di(C -C )alkylsalicylic acid 33% m. of 3-(C -C )alkyl-5-tert. butylsalicylic acid 28% 'm. of 3-tert. butyl-5-(C -C )alkylsalicylic acid Thus, of the para-substituted acids, approximately 38% m. were attached to the benzene nucleus by a quaternary carbon. The alkylsalicylic acids obtained were converted into calcium salts with a basicity of 50 and 200% w.

The catalyst was prepared as in Example I and the phenols were alkylated, converted into the corresponding alkylsalicylic acids and the basic calcium salts were prepared and recovered under conditions similar to those given in Example I.

I claim as my invention: 1. A mixture of dialkylsalicylic acids having at least one normal alkyl group with from 15-18 carbon atoms,

and atrleast'one tertiarybutyl group with the latter group 7 References Citedattached'to'the benzene nucleus1 through the quatfirnaryi UNITED STATESPATENTS carbon atom, atleast 60% oft 'eacid molecules aving an alkylgroup in the para position with respect to the g et h droxyl group, and at least 25% of the para-positioned 5 J 6 Y Y 3,148,158 9/1964 Shemck 252-450 alkyl'groups being tertiary butyl. Y Y

2. Alkaline earth metalsalts of a mixture of dialkyl- FOREIGN PATENTS salicylic acids having at least one normal alkyl group with 729,376 4/1953 Great Britain. from 15-18 carbon atoms and at least one tertiary butyl 759,346 10/1956 Great'Britain 2605 12 R group with the latter group attached to the benzene 10 OTHER, REFERENCES nucleus through the quaternary carbonlatom, at leastv 60%. of the acid moleculesrhaving an alkyl group; in the W A Benjamin Inc New York NY pp para position with respect to the hydroxyl group, and at- I least 25% of the para-positioned alkyl groups being 15 tertiary butyl. 1 LORRAINE A. WEINBERGER; Primary Examiner 3. The salts according to claim 2 wherein said salts are J. F, TERAPANE, A i t t E i basic and have a basicity from 25 to 225%. I S Cl X R 4. The salts according to claim 1 wherein the alkaline. 252 39 57 earth metal is calcium. 1 a 20 v Roberts et al., Basic Principles of'Organic Chemistry, 

